1. Field of the Invention
This invention relates to powder coating systems, and more particularly, to systems for spraying powder coating material onto objects such as automotive or other vehicle bodies.
2. Description of the Prior Art
The spraying of solid particulate materials for coating automotive and other vehicle bodies has been used for a number of years. The spraying can be accomplished using electrostatic spraying techniques in a spray booth which includes an elongated tunnel-like construction having an inlet for the ingress of the vehicle body, a coating application area, a curing or drying area in some designs, and an outlet for the egress of the vehicle body. Conditioned air is introduced in the spray booth by an air feed blower into a plenum chamber at the top of the booth and is directed downwardly toward the vehicle body moving through the booth. This flow of conditioned air picks up oversprayed powder coating material, i.e., material which does not adhere to the vehicle body, and is then drawn downwardly through the sides and/or floor of the booth by one of more air exhaust fans. Filters are provided to remove the particulate powder material from the air, and the resulting filtered or clean air is withdrawn from the booth for expulsion to atmosphere or for recirculation to the conditioned air supply while the recovered powder material is sent to a recovery system for classification and re-use.
This air flow system is generally effective in removing oversprayed powder from the booth. However, in the spraying of vehicle car bodies, the inside or cabin of the vehicle body can be partially isolated from this air flow, and much of the oversprayed powder in the vehicle cabin may not be significantly affected by this air flow system. As a result, oversprayed powder can remain aloft within the vehicle cabin for an extended period of time. When the powder in the vehicle cabin remains aloft after the vehicle body has left the spray zone, the suspended overspray may be conveyed into subsequent zones in the spray booth. This, in turn, can lead to contaminated downline processes or process equipment.